Aqueous alkyldiketene dispersions and their use as size for paper

ABSTRACT

Aqueous alkyldiketene dispersions comprising an alkyldiketene, cationic starch having an amylopectic content of at least 95% by weight and as anionic dispersants 
     (a) from 0.05 to 1.0% by weight of ligninsulfonic acid, condensates of naphthalenesulfonic acid and formaldehyde, sulfonated polystyrene, salts and mixtures of said polymers and (b) from 0.05 to 1.5% by weight of sulfuric monoesters of alcohols having at least 10 carbon atoms, phosphoric monoesters or diesters of alcohols having at least 10 carbon atoms, sulfuric monoesters of alkoxylated alcohols having at least 10 carbon atoms, phosphoric monoesters or diesters of alkoxylated alcohols having at least 10 carbon atoms, C 12  -C 30  -alkylsulfonic acids, salts and mixtures of said compounds 
     can be used as body size in the manufacture of paper, paperboard and cardboard and for making cellulose fibers hydrophobic.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of a PCT application filedunder 35USC371 on Oct. 25, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to aqueous alkyldiketene dispersionscomprising an alkyldiketene, cationic starch and anionic dispersants,and to the use of the aqueous alkyldiketene dispersions as body size inthe manufacture of paper, paperboard and cardboard and also for makingcellulose fibers hydrophobic.

2. Description of the Background

EP-B-0 353 212 discloses sizes in the form of aqueous emulsionscomprising a hydrophobic cellulose-reactive size, e.g. fattyalkyldiketene, and a cationic starch having an amylopectin content of atleast 85% and a degree of cationization (D.S.) of from 0.045 to 0.4. Theproportion of amylopectin in the cationic starch is preferably from 98to 100%.

EP-B-0 369 328 discloses aqueous alkyldiketene dispersions containing upto 30% by weight of ketenedimer. Further essential constituents of thesealkyldiketene dispersions are cationic starch, preferably cationic waxymaize starch, aluminum sulfate, carboxylic acids having from 1 to 10carbon atoms, and sulfonates such as the sodium salt of ligninsulfonicacid or condensation products of formaldehyde and naphthalenesulfonicacids.

EP-B-0 437 764 discloses stabilized aqueous alkyldiketene dispersionscomprising, apart from an alkyldiketene, a protective colloid and anester of a long-chain carboxylic acid and a long-chain alcohol.Preferred protective colloids are cationic starches. In addition,sorbitan esters, soaps, synthetic detergents and thickeners such aspolymers of acrylamide, vinylpyrrolidone and N-vinyl-2-methylimidazolinecan also be used.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide novel aqueousalkyldiketene dispersions which have a long shelf life and, if possible,are shear stable and have a high concentration of dispersedalkyldiketene.

We have found that this object is achieved by means of aqueousalkyldiketene dispersions comprising an alkyldiketene, cationic starchand anionic dispersants, if the cationic starch has an amylopectincontent of at least 95% by weight and the anionic dispersants present inthe dispersions are

(a) from 0.05 to 1.0% by weight of ligninsulfonic acid, condensates ofnaphthalenesulfonic acid and formaldehyde, sulfonated polystyrene, saltsand mixtures of said polymers and

(b) from 0.05 to 1.5% by weight of sulfuric monoesters of alcoholshaving at least 10 carbon atoms, phosphoric monoesters or diesters ofalcohols having at least 10 carbon atoms, sulfuric monoesters ofalkoxylated alcohols having at least 10 carbon atoms, phosphoricmonoesters or diesters of alkoxylated alcohols having at least 10 carbonatoms, C₁₂ -C₃₀ -alkylsulfonic acids, salts and mixtures of saidcompounds.

The present invention also provides for the use of the above-describedaqueous alkyldiketene dispersions as body size in the manufacture ofpaper, paperboard and cardboard and for making cellulose fibershydrophobic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preparation of the aqueous alkyldiketene dispersions preferablystarts from C₁₄ -C₂₂ -alkyldiketenes or from mixtures of suchalkyldiketenes. Alkyldiketenes are known and commercially available.They are prepared, for example, from the corresponding carboxylic acidchlorides by elimination of hydrogen chloride using tertiary amines.Suitable fatty alkyldiketenes are, for example, tetradecyldiketene,palmityldiketene, stearyldiketene and behenyldiketene. Also suitable arediketenes having different alkyl groups, e.g. stearylpalmityldiketene,behenylstearyldiketene, behenyloleyldiketene or palmitylbehenyldiketene.Preference is given to using stearyldiketene, palmityldiketene,behenyldiketene or mixtures of stearyldiketene and palmityldiketene ormixtures of behenyldiketene and stearyldiketene. The diketenes arepresent in the aqueous emulsions in concentrations of, for example, from10 to 45% by weight, preferably from 15 to 25% by weight.

The alkyldiketenes are emulsified in water in the presence of cationicstarch which, according to the present invention, has an amylopectincontent of at least 95% by weight, preferably from 98 to 100% by weight.Such starches can be obtained, for example, by fractionation ofcustomary native starches or by cultivating plants which producevirtually pure amylopectin starch, cf. Gunther Tegge, Starke undStarkederivate, Hamburg, Bers-Verlag 1984, pages 157 to 160. Cationicstarches having an amylopectin content of at least 95% by weight,preferably from 98 to 100% by weight, are commercially available. Theamylopectin starches have a branched structure and a high degree ofpolymerization. The molecular weights (number average) are, for example,from 200 million to 400 million. For waxy maize starch having anamylopectin content of from 99 to 100%, the literature givesnumber-average molecular weights of about 320 million. According to thepresent invention, the cationized starches used have an amylopectincontent of at least 95%. The degree of cationization of the starch isdescribed by means of the degree of substitution (D.S.). This valuegives the number of cationic groups per monosaccharide unit in thecationic starch. The degree of substitution (D.S.) of the cationicstarches is, for example, from 0.010 to 0.150, preferably from 0.02 to0.1. In most cases it is below 0.045, e.g. the particularly preferredcationic starches have a degree of substitution (D.S.) of from 0.020 to0.040.

The cationization of the starch containing at least 95% by weight ofamylopectin is carried out by introducing groups containing tertiary orquaternary nitrogen atoms, e.g. by reacting suitable starches, inparticular waxy maize starch, with dialkylaminoalkyl epoxides of theformula ##STR1## or with dialkylaminoalkyl chlorides of the formula##STR2## or preferably with epoxide-containing quaternary ammonium saltsof the formula ##STR3## or the corresponding halohydrins of the formula##STR4##

In the formulae I to IV, the substituents R², R³ and R⁴ are alkyl, aryl,aralkyl or hydrogen, R¹ is an alkylene group, e.g. C₁ -C₆ -alkylene.Examples of such compounds are3-chloro-2-hydroxy-propyltrimethylammonium chloride orglycidyltrimethylammonium chloride.

Apart from the preferred waxy maize starch, other useful starches arewaxy potato starch, waxy wheat starch or mixtures of said starches, ineach case in cationized form.

The cationic starches having amylopectin contents of at least 95% arepresent to an extent of from 0.5 to 5% by weight, preferably from 1 to3% by weight, in the aqueous alkyldiketene dispersion. The finelydivided, aqueous alkyldiketene dispersions are usually prepared by firstconverting the starches containing at least 95% of amylopectin into awater-soluble form. This can be achieved, for example, by means ofoxidative or hydrolytic degradation in the presence of acids or bysimply heating the cationic starches. The digestion of the starch ispreferably carried out in a Jet digester at from 100 to 150° C. In theaqueous solution of the cationic starch having a minimum amylopectincontent of at least 95% by weight obtainable in this way, there is thendispersed at least one C₁₄ -C₂₂ -alkyldiketene, preferably in thepresence of the dispersants (a) and (b) at above 70° C., e.g. in therange from 70 to 85° C. However, if desired, the alkyldiketenes can alsobe dispersed in the presence of at least one dispersant (a) or (b). Toobtain the dispersions of the present invention, the other dispersant isthen added and the dispersion is homogenized if necessary. However, thedispersants (a) and (b) can also be added to the dispersion obtainedafter dispersing the alkyldiketene in the abovedescribed aqueoussolution of a cationic starch, with the mixture then usually beingfurther subjected to a high shear rate, e.g. in a homogenizer atpressures of up to 1000 bar. The alkyldiketene dispersion is then cooledso that the alkyldiketenes are present in solid form. This gives finelydivided aqueous alkyldiketene dispersions having a mean particlediameter of, for example, from 0.5 to 2.5 μm, preferably from 0.8 to 1.5μm.

Suitable dispersants (a) are ligninsulfonic acid, condensates offormaldehyde and naphthalenesulfonic acids, polymers containingstyrenesulfonic acid groups, for example sulfonated polystyrenes, or thealkali metal and/or ammonium salts of said compounds containing sulfonicacid groups. They are present in the aqueous alkyldiketene dispersion inamounts of from 0.05 to 1.0% by weight, preferably from 0.01 to 0.5% byweight. The aqueous alkyldiketene dispersions contain as dispersant (b)from 0.05 to 1.5% by weight of sulfuric monoesters of alcohols having atleast 10 carbon atoms, phosphoric monoesters or diesters of alcoholshaving at least 10 carbon atoms, sulfuric monoesters of alkoxylatedalcohols having at least 10 carbon atoms, phosphoric monoesters ordiesters of alkoxylated alcohols having at least 10 carbon atoms, C₁₂-C₃₀ -alkylsulfonic acids, salts and mixtures of said compounds. Thesulfuric monoesters are preferably derived from alcohols having from 12to 30 carbon atoms or from mixtures of such alcohols. Suitable alcoholsfor the preparation of sulfuric esters are, for example, lauryl alcohol,palmityl alcohol, stearyl alcohol, behenyl alcohol and the long-chainalcohols obtainable by the oxo process.

The abovementioned alcohols having at least 10 carbon atoms are alsosuitable for preparing phosphoric monoesters or diesters which arelikewise dispersants. The alcohols preferably used for preparing thephosphoric monoesters and diesters usually have from 12 to 30 carbonatoms.

The alcohols having at least 10 carbon atoms, preferably those havingfrom 12 to 30 carbon atoms, can also be reacted in alkoxylated form withsulfuric acid or phosphoric acid to give sulfuric monoesters orphosphoric monoesters or diesters. The alcohols containing at least 10carbon atoms can, for example, be alkoxylated with ethylene oxide,propylene oxide and/or butylene oxide. Preference is given to usingethoxylated alcohols for preparing the dispersants (b). From 1 to 25mol, preferably from 1 to 10 mol, of at least one alkylene oxide,preferably ethylene oxide, are used per mol of alcohol. The appropriatealcohols can also be reacted with a plurality of alkylene oxides to formblock copolymers containing, for example, blocks of ethylene oxide andpropylene oxide or blocks of ethylene oxide, propylene oxide andbutylene oxide or blocks of ethylene oxide and butylene oxide. The orderof the blocks can here be any desired. Likewise, it is possible toprepare alkoxylated alcohols which have the alkylene oxide unitsrandomly distributed, for example by reacting a mixed gas of ethyleneoxide and propylene oxide with the long-chain alcohols. Preference isgiven to using alcohols having from 12 to 30 carbon atoms which havebeen reacted with from 2 to 8 mol of ethylene oxide per mol of alcohol.

Further suitable dispersants (b) are C₁₂ -C₃₀ -alkylsulfonic acids.Preference is given to C₁₈ -C₂₂ -alkylsulfonic acids. Apart from theabovementioned compounds containing free acid groups, it is alsopossible to use as dispersants (a) and (b) the salts of the acidcompounds described above under (a) and (b), for example alkali metal,alkaline earth metal and ammonium salts. The dispersants (a) and (b) areparticularly preferably in the form of sodium salts. The potassium,lithium, magnesium, calcium and barium salts are also suitable.Preferred aqueous alkyldiketene dispersions comprise, for example,cationic starch having an amylopectin content of at least 98% by weightand a degree of substitution (D.S.) of from 0.02 to 0.1 and, as anionicdispersants,

(a) from 0.1 to 0.5% by weight of ligninsulfonic acid, condensates ofnaphthalenesulfonic acid and formaldehyde, sulfonated polystyrene, saltsand mixtures of said polymers and

(b) from 0.1 to 1.0% by weight of sulfuric monoesters of alcohols havingat least 12 carbon atoms, phosphoric monoesters or diesters of alcoholshaving at least 12 carbon atoms, sulfuric monoesters of alkoxylatedalcohols having at least 12 carbon atoms, phosphoric monoesters ordiesters of alkoxylated alcohols having at least 12 carbon atoms, C₁₂-C₃₀ -alkylsulfonic acids, salts and mixtures of said compounds.

Particular preference is given to aqueous alkyldiketene dispersionswhich comprise

(a) from 0.1 to 0.5% by weight of the sodium and/or potassium salts ofligninsulfonic acid or of condensates of naphthalenesulfonic acid andformaldehyde and

(b) from 0.1 to 1.0% by weight of the sodium and/or potassium salts ofsulfuric monoesters of alcohols having from 16 to 22 carbon atoms and/orsodium and/or potassium salts of C₁₆ -C₂₂ -alkylsulfonic acids.

In the preparation of the alkyldiketene emulsions, it is possible tomake concomitant use of not only the cationic waxy starches but also, ifdesired, other customary protective colloids which have previously beenused in the preparation of alkyldiketene emulsions, e.g. water-solublecellulose ethers, polyacrylamides, polyvinyl alcohols,polyvinylpyrrolidones, polyamides, polyamidoamines and mixtures of saidcompounds. The dispersions of the present invention can, if desired,contain further materials which are customary in alkyldiketenedispersions, e.g.

C₁ -C₁₀ -carboxylic acids such as formic acid, acetic acid or propionicacid. The acids are, if present in the alkyldiketene dispersions, usedin amounts of from 0.01 to 1% by weight. The alkyldiketene dispersionscan, if desired, additionally contain customary biocides which can beemployed in amounts of up to 1% by weight.

The aqueous alkyldiketene dispersions of the present invention arestorage stable and compared with the highly concentrated aqueousalkyldiketene dispersions known hitherto also shear stable. They can beprocessed as well as low-concentration aqueous alkyldiketenedispersions.

In the examples, the percentages are by weight and, if not otherwiseindicated, parts are by weight.

EXAMPLE 1

A 2.5% strength aqueous solution of a cationic starch having anamylopectin content of 98% and a D.S. of 0.03 is first prepared bysuspending the required amount of starch in water, heating thissuspension to 95° C. and stirring it at this temperature until a clearsolution has been formed.

After cooling to 85° C., 84 parts of the above-described 2.5% strengthaqueous solution of starch are admixed with 15.8 parts of a melt ofstearyldiketene heated to 85° C., 0.1 part of the sulfuric monoester ofan addition product of 3.5 mol of ethylene oxide and 1 mol ofhexadecanol and 0.1 part of ligninsulfonate. The mixture is subsequentlytreated for 1 minute with an Ultraturrax and then homogenized twice in ahomogenizer (LAB 100) at a pressure of 200 bar. After cooling to roomtemperature, a stearyldiketene dispersion having a solids content of18.1% is obtained.

EXAMPLE 2

A 3.25% strength aqueous solution of a cationic starch having anamylopectin content of 98% and a D.S. of 0.035 is first prepared bysuspending the required amount of starch in water, heating thissuspension to 95° C. and stirring it at this temperature until a clearsolution has been formed.

77 Parts of the 3.25% strength aqueous starch solution thus prepared areadmixed at 85° C. with 20 parts of a melt of stearyldiketene heated to85° C., 0.3 part of sodium ligninsulfonate and 0.2 part of thephosphoric monoester of hexadecanol. The mixture is subsequently treatedfor 1 minute with an Ultraturrax and then homogenized twice in ahomogenizer (LAB 100) at a pressure of 200 bar. After cooling to roomtemperature, a stearyldiketene dispersion having a solids content of 23%is obtained.

EXAMPLE 3

A 3.90% strength aqueous solution of a cationic starch having anamylopectin content of 98% and a D.S. of 0.03 is first prepared bysuspending the required amount of starch in water, heating thissuspension to 95° C. and stirring it at this temperature until a clearsolution has been formed.

76 Parts of the 3.90% strength aqueous starch solution thus prepared areadmixed at 85° C. with 20 parts of a melt of stearyldiketene heated to85° C., 0.1 part of a commercial naphthalenesulfonic acid-formaldehydecondensate and 0.5 part of the sodium salt of hexadecylsulfonic acid.The mixture is treated for 1 minute with an Ultraturrax and thenhomogenized twice in a laboratory homogenizer at a pressure of 200 bar.After cooling to room temperature, a stearyldiketene dispersion having asolids content of 23.6% is obtained.

EXAMPLE 4

Example 3 is repeated with the exception that the aqueous starchsolution is prepared in a Jet digester at 135° C. After homogenizationand cooling to room temperature, a diketene dispersion having a solidscontent of 23.6% is obtained.

EXAMPLE 5

A 4.20% strength aqueous solution of a cationic starch having anamylopectin content of 98% and a D.S. of 0.041 is first prepared bysuspending the required amount of starch in water and converting thesuspension into a solution in a Jet digester at 135° C.

After cooling to 85° C., 71 parts of the 4.20% strength aqueous starchsolution thus obtained are admixed with 25 parts of a melt ofstearyldiketene heated to 85° C., 0.3 part of a commercialnaphthalenesulfonic acid-formaldehyde condensate and 0.5 part of thesodium salt of hexadecylsulfonic acid. The mixture is treated for 1minute with an Ultraturrax and then homogenized twice in a laboratoryhomogenizer at a pressure of 200 bar. After cooling to room temperature,a stearyldiketene dispersion having a solids content of 28.8% isobtained.

EXAMPLE 6

Example 5 is repeated with the exception that 0.2 part of sodiumligninsulfonate and 0.7 part of the sulfuric monoester of octadecanolare used as dispersant in place of the amounts of anionic dispersantsindicated in Example 5. A stearyldiketene dispersion having a solidscontent of 28.9% is obtained.

EXAMPLE 7

A 3.90% strength aqueous solution of a cationic starch having anamylopectin content of 98% and a D.S. of 0.035 is first prepared bysuspending the required amount of starch in water and converting thesuspension into a solution by treatment in a Jet digester at 125° C.

After cooling to 85° C., 76 parts of the 3.9% strength aqueous starchsolution thus obtained is admixed with 20 parts of a melt ofstearyldiketene heated to 85° C., 0.3 part of a commercialnaphthalenesulfonic acid-formaldehyde condensate and 0.2 part of thesulfuric monoester of an addition product of 5 mol of ethylene oxide and1 mol of octadecanol. The mixture is then treated for 1 minute with anUltraturrax and subsequently sheared twice in a laboratory homogenizerat a pressure of 200 bar. After cooling to room temperature, astearyldiketene dispersion having a solids content of 23.5% is obtained.

EXAMPLE 8

A 5.30% strength aqueous solution of a cationic starch having anamylopectin content of 98% and a D.S. of 0.035 is first prepared bysuspending the required amount of starch in water and converting thesuspension into a solution by treatment in a Jet digester at 135° C.

After cooling to 85° C., 66 parts of the 5.30% strength starch solutionare admixed with 30 parts of a melt of stearyldiketene heated to 85° C.,0.3 part of a commercial naphthalenesulfonic acid-formaldehydecondensate and 0.4 part of the monoester of phosphoric acid and anaddition product of 6 mol of ethylene oxide and 1 mol of octadecanol.The mixture is treated for 1 minute with an Ultraturrax and subsequentlysheared twice in a laboratory homogenizer at a pressure of 200 bar.After cooling to room temperature, a stearyldiketene dispersion having asolids content of 34.2% is obtained.

Comparative Example 1

A 3.25% strength aqueous dispersion of a cationic starch having anamylopectin:amylose ratio of 3:1 and a D.S. of 0.033 is first preparedby suspending the required amount of starch in water and converting thesuspension into a solution by stirring at 95° C.

After cooling to 85° C., 77 parts of a 3.25% strength aqueous starchsolution thus obtained are admixed with 20 parts of a melt ofstearyldiketene heated to 85° C. and 0.3 part of sodium ligninsulfonate.The mixture is treated for 1 minute with an Ultraturrax and then shearedtwice in a laboratory homogenizer at a pressure of 250 bar. Aftercooling to room temperature, a stearyldiketene dispersion having asolids content of 22.8% is obtained.

Comparative Example 2

A 4.20% strength aqueous solution of a cationic starch having anamylopectin:amylose ratio of 3:1 and a D.S. of 0.040 is first prepared.For this purpose, the required amount of starch is suspended in waterand brought into solution by heating to 95° C.

After cooling to 85° C., 71 parts of a 4.20% strength aqueous starchsolution thus obtained are admixed with 25 parts of a melt ofstearyldiketene heated to 85° C. and 0.3 part of a commercialnaphthalenesulfonic acid-formaldehyde condensate. The mixture is treatedfor 1 minute with an Ultraturrax and subsequently sheared twice in alaboratory homogenizer at a pressure of 250 bar. After cooling to roomtemperature, a stearyldiketene dispersion having a solids content of28.3% is obtained.

Comparative Example 3

Prior art as described in EP-B-0 437 764

A 2% strength aqueous suspension of a commercial cationic starch (D.S.of 0.02) is prepared by suspending the required amount of cationicstarch in water and is then admixed with sufficient sulfuric acid tobring the pH to 3. The starch suspension is then heated to 95° C. andstirred for 1 hour at this temperature. An aqueous starch solution isobtained.

78 Parts of the 2% strength aqueous starch solution thus prepared areadmixed at 85° C. with a melt comprising 20 parts of stearyldiketene and2 parts of oleyl stearate heated to 90° C. and the mixture is treatedfor 3 minutes with an Ultraturrax. The emulsion is subsequentlyhomogenized twice at 70° C. in a laboratory homogenizer under a pressureof 150 bar and is then cooled to room temperature. A stablestearyldiketene dispersion having a solids content of 23.5% is obtained.

Comparative Example 4

Prior art as described in EP-B-0 353 212

Suspending 125 parts of a cationic starch having an amylopectin contentof 99% and a D.S. of 0.072 in 2500 parts of water and subsequent heatinggave a clear, highly viscous, 4.76% strength aqueous starch solution.This mixture was admixed with 20 parts of the sodium salt of sulfonatedpolystyrene in 500 parts of stearyldiketene while stirring. The coarsedispersion thus obtained was sheared in a homogenizer at 200 bar, cooledand subsequently diluted to a solids content of 12.9% by addition ofwater.

Comparative Example 5

Prior art as described in EP-B-0 369 328

A 5.05% strength aqueous solution of cationic starch (Amaizo 2187) isfirst prepared by suspending 67.5 g of the commercial starch having amoisture content of 13% and 6 g of sodium ligninsulfonate in 1090.2 g ofwater and heating the suspension. 15 g of a 5% strength aqueous aceticacid solution and 300 g of stearyldiketene are subsequently added. Thecoarse suspension thus obtained is cooled to 70° C. and homogenized in alaboratory homogenizer under a pressure of 200 bar. The emulsion is,while still hot, admixed while stirring with 19.6 g of a 5% strengthaluminum sulfate solution and the mixture is cooled to 25° C. Thestearyldiketene dispersion has a solids content of 24.5%.

The table shows the viscosities of the aqueous alkyldiketene dispersionsdirectly after preparation and after storage for 90 days at 25° C. Thetable also gives sizing values obtained using the alkyldiketenedispersions from the examples and comparative examples with thefollowing composition model: wood-free, 100% bleached birch sulfatehaving a degree of milling of 35° Schopper-Riegler, 40% of chalk and0.025% of a commercial high molecular weight polyacrylamide as retentionagent. Paper sheets having a weight per unit area of 80 g/m² wereproduced on a Rapid-Kothen sheet maker. The ash content was 17%. Thesizing values were determined after storage for 48 hours at 23° C.

To obtain comparable results, 0.1% of the alkyldiketene dispersionsprepared in the examples or comparative examples, based on solidalkyldiketene, was in all cases added to the composition model.

                  TABLE                                                           ______________________________________                                                Viscosity [mpas]        Ink                                                   directly after                                                                         after storage      floatation                                        preparation of                                                                         of the dispersion  time                                              the dispersion                                                                         for 90 days Cobb   [min]                                     ______________________________________                                        Example                                                                       1         14.1       87.6        24   60                                      2         19.7       78.3        23   55                                      3         23.2       152.5       26   56                                      4         18.6       84.0        25   60                                      5         34.7       248.7       24   60                                      6         31.6       212.4       26   53                                      7         25.9       189.9       28   60                                      8         54.8       545         28   52                                      Comparative                                                                   example                                                                       1         89.8       >2000       25   60                                      2         237.1      -.sup.1)    26   48                                      3         265.2      -.sup.1)    26   53                                      4         14.0       65.6        25   55                                      5         33.2       217.5       27   55                                      ______________________________________                                         .sup.1) Viscosity could not be determined because the mixture was solid  

We claim:
 1. An aqueous alkyldiketene dispersion comprising analkyldiketene, cationic starch and anionic dispersants, wherein thecationic starch has an amylopectin content of at least 95% by weight andthe anionic dispersants present in the dispersion are(a) from 0.05 to1.0% by weight of ligninsulfonic acid, condensates ofnaphthalenesulfonic acid and formaldehyde, sulfonated polystyrene, saltsand mixtures of said polymers and (b) from 0.05 to 1.5% by weight ofsulfuric monoesters of alcohols having at least 10 carbon atoms,phosphoric monoesters or diesters of alcohols having at least 10 carbonatoms, sulfuric monoesters of alkoxylated alcohols having at least 10carbon atoms, phosphoric monoesters or diesters of alkoxylated alcoholshaving at least 10 carbon atoms, C₁₂ -C₃₀ -alkylsulfonic acids, saltsand mixtures of said compounds.
 2. An aqueous alkyldiketene dispersionas claimed in claim 1, wherein the cationic starch has an amylopectincontent of at least 98% by weight and a degree of substitution (D.S.) offrom 0.02 to 0.1 and the anionic dispersants present are(a) from 0.1 to0.5% by weight of ligninsulfonic acid, condensates ofnaphthalenesulfonic acid and formaldehyde, sulfonated polystyrene, saltsand mixtures of said polymers and (b) from 0.1 to 1.0% by weight ofsulfuric monoesters of alcohols having at least 12 carbon atoms,phosphoric monoesters or diesters of alcohols having at least 12 carbonatoms, sulfuric monoesters of alkoxylated alcohols having at least 12carbon atoms, phosphoric monoesters or diesters of alkoxylated alcoholshaving at least 12 carbon atoms, C₁₂ -C₃₀ -alkylsulfonic acids, saltsand mixtures of said compounds.
 3. An aqueous alkyldiketene dispersionas claimed in claim 1 comprising cationic waxy maize starches.
 4. Anaqueous alkyldiketene dispersion as claimed in claim 1, wherein thedegree of substitution (D.S.) of the cationic starches is below 0.045.5. An aqueous alkyldiketene dispersion as claimed in claim 1, whereinthe degree of substitution (D.S.) of the cationic starches is from 0.02to 0.040.
 6. An aqueous alkyldiketene dispersion as claimed in claim 1,comprising(a) from 0.1 to 0.5% by weight of the sodium and/or potassiumsalts of ligninsulfonic acid or of condensates of naphthalenesulfonicacid and formaldehyde and (b) from 0.1 to 1.0% by weight of the sodiumand/or potassium salts of sulfuric monoesters of alcohols having from 16to 22 carbon atoms and/or sodium and/or potassium salts of C₁₆ -C₂₂-alkylsulfonic acids.
 7. A method of manufacturing paper, paperboard andcardboard, comprising:applying the aqueous alkyldiketene dispersion ofclaim 1 to said paper, paperboard or cardboard during its manufacture.8. A method of making cellulose fibers hydrophobic comprising:applyingthe aqueous alkyldiketene dispersion of claim 1 to cellulose fibersthereby hydrophobicizing the cellulose fibers.